Diagnostic Aids

WARNING: This page is about a different car, the 2009 GMC Yukon, 2009 Chevrolet Tahoe, 2009 Chevrolet Suburban, and 2009 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

A short to ground on the 4 low indicator control circuit will cause the 4 Low indicator to remain ON at all times.
An open or high resistance will cause the 4 Low indicator to be inoperative during the 2 second bulb inspection.
An open in the indicator dimming control circuit will cause the 2 High, AWD, 4 High and 4 Low mode indicators to be inoperative during the 2 second bulb inspection.